Holliston is a New England town in Middlesex County, Massachusetts, United States in the Greater Boston area. The population was 13,547 at the 2010 census. It is part of the Massachusetts region, located due west of Boston, that is known as the MetroWest. Holliston is the only town in Middlesex County that borders both Norfolk and Worcester counties.

Once populated by factories and farms up until the latter part of the nineteenth century, Holliston has now transformed itself into a bedroom community for Boston and the Route 128 and Route 495 technology belts. Holliston is known for its quaint Town Center with its Fiske's General Store, the Superette, numerous antique shops and boutiques, Carnegie public library, town hall, and white-steepled churches. Numerous white antique colonial, Greek revival, and Victorian homes with well-manicured lawns dot the landscape along Washington Street (Massachusetts Route 16), with Holliston Center and the Town Green wedged in between—a scene reminiscent of the distinctive New England character.

According to the United States Census Bureau, the town has a total area of 19.0 square miles (49 km2), of which 18.7 square miles (48 km2) is land and 0.3 square miles (0.78 km2) is water. Water covers 1.73% of the town's total area. The Charles River passes near the southern region of town.

As of the census of 2000, there were 13,801 people, 4,795 households, and 3,842 families residing in the town. The population density was 737.8 people per square mile (284.8/km˛). There were 4,868 housing units at an average density of 260.2 per square mile (100.5/km˛).